1. Field of the Invention
This invention relates to polyethercyclicpolyols having high molecular weights and to the preparation thereof. In particular, the invention relates to the preparation of polyethercyclicpolyols which, due to improved molecular properties and characteristics, permit the preparation of improved drilling fluids.
2. Description of the Prior Art
Water-based drilling fluids of the prior art comprise water, clays or polymers, and various drilling fluid additives which control the physical, chemical and/or rheological properties of drilling fluids in wellbores. It is desirable that such drilling fluid additives inhibit formation of gas hydrates, prevent shale dispersion, reduce swelling of the formation to improve wellbore stability, reduce fluid loss, and reduce filter cake thickness. In order to perform these functions as drilling fluid additives, it is theorized, although the present invention is not limited to this theory, that an ideal polymeric drilling fluid additive would contain large water soluble molecules and have relatively limited crosslinking in spite of high molecular weight. It is difficult to produce polymeric molecules of this type of high molecular weight which do not have extensive crosslinking, and the prior art has been unsuccessful in producing such an ideal drilling fluid additive which performs the desired functions. Accordingly, the present invention provides a process which overcomes these and other problems in the art as more particularly disclosed hereinafter, and which produces polyethercyclicpolyols of significantly improved characteristics as drilling fluid additives.